Oceanic and atmospheric excitation of the Chandler wobble

The excitation mechanism of the Chandler wobble (CW) is investigated by examining the power spectra of oceanic angular momentum (OAM) excitation (1985-1995) and two series of atmospheric angular momentum (AAM) excitation. The power spectra are then compared with those of the observed excitation derived from the polar motion of COMB2000 series for different periods of time. The results show that the excitation from OAM can provide approximately 64 per cent of the required energy of the observed CW excitation, while the energy from AAM excitation is comparable with that of the observed CW excitation sometimes, but it is far less than that of the observed one at other times. The multitaper coherence analysis method is also used to investigate the relationship between the observed CW excitation and the geophysical excitation derived from OAM and AAM in the frequency domain. The results show that there is a high coherence (0.52) between the OAM excitation and the observed one during 1985-1995, while large fluctuations of the coherence and linear trend of the coherent phases exist between the AAM excitation and the observed one during 1962-2000. Some analyses are also made concerning the effects of different CW periods and quality factor (Q) on the CW excitation.